How ketones affects performance and recovery for running, OCR, and endurance sports
Thomas Solomon, PhD.
Updated onReading time approx 7 minutes (1400 words).
What you’ll learn:
Ketones are “backup” fuels your body can burn for energy (ATP) when carbohydrate stores (glycogen) are empty and blood sugar levels are low.
Based on current studies, ketone supplements don’t meaningfully improve endurance performance or recovery. Ultra-distance racing might be a special case, but we don’t have strong data yet.
Curious about the how and why? Scroll down for the details, the nuances, and the nerdy bits.
The information I provide is not medical advice. Supplements can have side effects and might interact with other drugs, nutrients, and medical conditions. If you are unsure, always consult your doctor to ensure a specific supplement is safe for you to use.
What are ketones?
Ketones are small molecules your body makes — acetate, acetoacetate, and β-hydroxybutyrate (also called 3-hydroxybutyrate). In everyday life they hover in your blood in tiny amounts (below 0.5 millimoles per litre, 0.5 mM). Levels rise when your carb tank is low. That state is called ketosis and usually sits around 0.5 to 3 mM. You might reach ketosis during a long fast (about 12 hours without calories), a very long workout, or a very low-carb diet (under 50 grams per day). That’s called “physiological” ketosis, which is safe and normal, and not the same as ketoacidosis, which is a dangerous medical emergency seen in some people with diabetes when ketones can climb toward 10 mM or higher. Different thing, different vibe, call a doctor for that one.
When carbs are scarce, your liver turns fat (triglycerides and fatty acids) into ketones and ships them around the body—especially to your brain—so you can keep moving and thinking. Besides the physiological/pathophysiological events described above, you can also raise blood ketones by drinking them (see here & here). Products usually contain a ketone ester (for example, (R)-3-hydroxybutyl (R)-3-hydroxybutyrate) or a ketone precursor like R-1,3-butanediol. Some evidence shows that a single dose of ketones can decrease blood glucose concentrations, showing its potential for diabetes treatment. There are also studies showing how ketone supplementation may affect appetite and cognitive function in humans, but more high-quality studies are needed before we get carried away.
The first published exercise study using ketone supplementation reported higher fat burning and a faster time trial even when muscle glycogen levels were normal and carbohydrates were ingested during exercise (see Cox et al. 2016). Consequently, the media has gone nuts, athlete/team sponsorships are rife, and several companies started selling ketone-containing products. The most heavily marketed ketone supplement is the “drinkable ketone” from HVMN — KetoneIQ — which contains a ketone precursor (R-1,3-butanediol) that is converted to β-hydroxybutyrate (a ketone) in the body. If you follow pro cycling, you will hear a lot about this product because they sponsor a large number of the pro teams. But sexy marketing does not equal proof of benefit. So…
What is the scientific evidence on the impact of ketones on athletic performance?
Ketones are generally safe to consume for healthy adults.
Meta-analysesA meta-analysis quantifies the overall effect size of a treatment by compiling effect sizes from all known studies of that treatment. report that short-term (single dose) or longer-term (daily) use of ketone esters or ketone precursors doesn’t improve endurance performance during time-to-exhaustion and time trial tests that range from about 90 seconds to 2 hours (see Brookset al. 2022 and Valenzuela et al. 2020).
Across studies, ketone esters and ketone precursors perform about the same—neither reliably boosts endurance.
However, its difficult to make firm conclusions about the effects of ketones because of the large variability in designs and effects between studies (see Margolis et al. 2019, Brookset al. 2022 and Valenzuela et al. 2020). For example, test durations differ widely, fed versus fasted states vary, and many trials pair ketones with carbohydrate intake. When small benefits do turn up, they tend to show up with higher doses that raise blood β-hydroxybutyrate above about 2 mM (see Figure 4 in Margolis et al. 2020). However, because we don’t yet have good dose-response studies, that is also a shakey observation, not a rule.
So, the ketone supplement world seems to be one of those “first paper dogma” stories where the first paper published (Cox et al. 2016 Cell Metabolism) found a beneficial effect but subsequent studies did not confirm the findings yet the media kept echoing the narrative of “ketones are the bomb”.
That aside, there are some unanswered questions:
There’s currently no meta-analysisA meta-analysis quantifies the overall effect size of a treatment by compiling effect sizes from all known studies of that treatment. on strength outcomes with ketone supplements.
There’s also no meta-analysis on ultra-distance performance. Because ketones matter more when glycogen and blood glucose are low, ultras are a logical testing ground but right now that’s a big question mark. Because ketones can fuel the brain when glucose is scarce (Cunnane et al.), it has been proposed that ketones might help cognition under stress (fasting, hypoxia, hard exercise). Some rodent studies (see Pawlosky et al., Murray et al., Ahmad et al.) and a few human trials show benefits (see Evans et al., McClure et al., Waldman et al., Quinones et al., Kackley et al., Walsh et al., Krolak-Salmon et al.), but several others don’t (see Waldman et al., Waldman et al., McClure et al.) — so, more research is needed before we claim sharper late-race decision-making.
If you choose to use a ketone supplement, a reasonable dose is:
A pre-exercise dose that lifts blood β-hydroxybutyrate to at least 2 mM. Note: that suggestion mirrors doses used in research; it is not a magic threshold that definitely causes a benefit.
Can ketones enhance athletic performance?
Ketones are unlikely to improve performance or recovery in typical endurance settings.
The effect sizeAn effect size is a standardized measure of the magnitude of an effect of an intervention. Unlike p-values, effect sizes show how large the effect is and indicate how meaningful it might be. Common effect size measures include standardised mean difference (SMD), Cohen’s d, Hedges’ g, eta-squared, and correlation coefficients. is trivial.
The effect appears to be similar between trained athletes and untrained folks, and between males and females; however, further research is needed in females because they are underrepresented among studies in this field.
Keep in mind: the studies are small and there is high heterogeneityHeterogeneity shows how much the results in different studies in a meta-analysis vary from each other. It is measured as the percentage of variation (the I2 value). A rule of thumb: if I2 is roughly 25%, that indicates low heterogeneity (good), 50% is moderate, and 75% indicates high heterogeneity (bad). High heterogeneity means there’s more variability in effects between studies and, therefore, a less precise overall effect estimate. (variability) in effects between studies, a moderate-to-high risk of biasRisk of bias in a meta-analysis refers to the potential for systematic errors in the studies included in the analysis. Such errors can lead to misleading/invalid results, and unreliable conclusions. This can arise because of issues with the way participants are selected (randomisation), how data is collected and analysed, and how the results are reported., and possible publication biasPublication bias in meta-analysis occurs when studies with significant results are more likely to be published than those with non-significant findings, leading to distorted conclusions. This bias can inflate effect sizes and misrepresent the true effectiveness of interventions, making it crucial to identify and correct for it in research.. So, the overall certainty of evidenceCertainty of evidence tells us how confident we are that the results reflect the true effect. It’s based on factors like study design, risk of bias, consistency, directness, and precision. Low certainty means more doubt and less confidence, and that future studies could easily change the conclusions. High certainty means that the current evidence is so strong and consistent that future studies are unlikely to change conclusions. is lowA low quality of evidence means that, in general, studies in this field have several limitations. This could be due to inconsistency in effects between studies, a large range of effect sizes between studies, and/or a high risk of bias (caused by inappropriate controls, a small number of studies, small numbers of participants, poor/absent randomisation processes, missing data, inappropriate methods/statistics). When the quality of evidence is low, there is more doubt and less confidence in the overall effect of an intervention, and new studies could easily change overall conclusions. The most effective way to enhance the quality of evidence is for scientists to conduct large, well-controlled, high-quality randomised controlled trials.. Therefore, additional high-quality randomised controlled trialsThe “gold standard” approach for determining whether a treatment has a causal effect on an outcome of interest. In such a study, a sample of people representing the population of interest is randomised to receive the treatment or a no-treatment placebo (control), and the outcome of interest is measured before and after exposure to the treatment and control. are needed to increase the certainty (confidence) in the overall effect sizes reported in meta-analysesA meta-analysis quantifies the overall effect size of a treatment by compiling effect sizes from all known studies of that treatment..
The nice part: ketones do not appear to have a detrimental effect on recovery or performance. So, if you like it and believe it works for you, give it a whirl. But, remember that time and money spent trying to improve your performance with something that has no obvious benefit might be better spent optimising your training load, sleep habits, and dietary/nutritional choices.
Additional trials on ultra-endurance performance are needed since this could feasibly be where ketones emerge to be beneficial, either direct performance benefits or effects on cognition function. Watch this space!
To minimise the risk of consuming a supplement that contains prohibited substances, only choose products that have been independently tested (e.g., Informed Sport). And, remember: Supplements do not make athletes and do not replace training; they're just the icing on a very well-baked cake. Before reaching for pills and potions, optimise your training load and dial in your sleep, nutrition, and rest.
How to use this: Treat ketones as an optional experiment for long training days or ultra builds. If you try them, take a pre-workout dose that reliably raises blood β-hydroxybutyrate above about 2 mM, test it in training (not race day first), and track how you feel, think, and perform. If there’s no clear benefit after a few trials, save your time and money to invest in things that definitely move the needle: good sleep, nutritious food, adequate rest, and an optimal training load.
Strengthen the fight for clean sport
Remember: You are the only person responsible for what goes in your body! Ignorance is not an excuse! Stay educated. Be informed.
Consult WADA’s prohibited list, cross-check your meds against the Global DRO drug reference list, and only choose supplements that have been tested by an independent body (e.g., Informed Sport or LabDoor).
Information you can trust. All content on Veohtu is meticulously researched and written by Thomas Solomon, PhD. He does not sell supplements, recovery products, or ad space, and he has no sponsorships, brand affiliations, or ambassador roles. Everything you read reflects his independent views, shaped solely by peer-reviewed scientific evidence — and that will never change.
Full list of meta-analyses examining ketones for performance.
Here are the meta-analyses I've summarised above:
Acute Ingestion of Ketone Monoesters and Precursors Do Not Enhance Endurance Exercise Performance: A Systematic Review and Meta-Analysis. Emma Brooks, Gilles Lamothe, Taniya S Nagpal, Pascal Imbeault, Kristi Adamo, Jameel Kara, Éric Doucet. Int J Sport Nutr Exerc Metab (2022).
Utility of Ketone Supplementation to Enhance Physical Performance: A Systematic Review. Margolis LM, O'Fallon KS. Adv Nutr (2020).
Acute Ketone Supplementation and Exercise Performance: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Valenzuela PL, Morales JS, Castillo-García A, Lucia A. Int J Sports Physiol Perform (2020).
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Who is Thomas Solomon?
My knowledge has been honed following 20+ years of running, cycling, hiking, cross-country skiing, lifting, and climbing, 15+ years of academic research at world-leading universities and hospitals, and 10+ years advising and coaching in athletic performance and lifestyle change.
I have a BSc in Biochemistry, a PhD in Exercise Science, and over 90 peer-reviewed publications in medical journals.
I'm also an ACSM-certified Exercise Physiologist (ACSM-EP), an ACSM-certified Personal Trainer (ACSM-CPT), a VDOT-certified Distance Running Coach, and a UKVRN Registered Nutritionist (RNutr).
Since 2002, I’ve conducted biomedical research in exercise and nutrition and have taught and led university courses in exercise physiology, nutrition, biochemistry, and molecular medicine.
And, with my personal experience of competing on the track (800m to 10,000m), the road (5 k to marathon), on the trails, and in the mountains, by foot, bicycle, cross-country ski, and during obstacle course races (OCR), I deeply understand what it's like to train and compete — I've been there, done it, and gotten sweat, mud, and tears on my t-shirt.
Disclaimer: I occasionally mention brands and products, but it is important to know that I don't sell recovery products, supplements, or ad space, and I'm not affiliated with / sponsored by / an ambassador for / receiving advertisement royalties from any brands. I have conducted biomedical research for which I’ve received research money from publicly-funded national research councils and medical charities, and also from private companies, including Novo Nordisk Foundation, AstraZeneca, Amylin, the A.P. Møller Foundation, and the Augustinus Foundation. I’ve also consulted for Boost Treadmills and Gu Energy on R&D grant applications, and I provide research and scientific writing services for Examine.com. Some of my articles contain links to information provided by Examine.com but I do not receive any royalties or bonuses from those links. Importantly, none of the companies described above have had any control over the research design, data analysis, or publication outcomes of my work. I research and write my content using state-of-the-art, consensus, peer reviewed, and published scientific evidence combined with my empirical evidence observed in practice and feedback from athletes. My advice is, and always will be, based on my own views and opinions shaped by the scientific evidence available. The information I provide is not medical advice. Before making any changes to your habits of daily living based on any information I provide, always ensure it is safe for you to do so and consult your doctor if you are unsure.